Burn-in system with measurement block accomodated in cooling block

ABSTRACT

A burn-in system enabling the temperatures of a large number of electronic devices differing in amount of self generated heat to be simultaneously reliably adjusted to a predetermined temperature, that is, a burn-in system bringing heater blocks having heaters, cooling blocks formed with channels able to carry a coolant, and sensor blocks having temperature sensors into contact with a plurality of DUTs mounted on a burn-in board and simultaneously performing a burn-in test on the plurality of DUTs, wherein each cooling block is formed with a first accommodating space and second accommodating space, each heater block is accommodated in a first accommodating space in a state maintaining clearance from the inside wall surfaces, and each sensor block is accommodated in a second accommodating space in a state maintaining clearance from the inside wall surfaces.

This application is a Divisional of co-pending application Ser. No.12/116,599, filed on May 7, 2008, which is a Divisional of applicationSer. No. 11/226,408, filed on Sep. 15, 2005, now U.S. Pat. No.7,397,258. The entire contents of each of the above-identifiedapplications are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a burn-in system for conducting aburn-in test for extracting initial defects of semiconductor integratedcircuits and other various types of electronic devices, moreparticularly relates to a burn-in system for simultaneously conducting aburn-in test on a large number of electronic devices. In countries whereincorporation by reference of other documents is allowed, the contentdescribed in the following application is incorporated into the presentapplication by reference and made part of the description of thisapplication.

Japanese Patent Application No. 2004-079623, filed on Mar. 19, 2004.

2. Description of the Related Art

As a burn-in system used for burn-in tests—a type of screening test forextracting initial defects of electronic devices and removing initiallymalfunctioning devices, there is known a system holding a burn-in boardmounting a large number of devices under test in a burn-in chamber,applying a predetermined voltage to impart electrical stress, andheating the air in this burn-in chamber to impart a predeterminedtemperature of thermal stress or a system not heating the air in theburn-in chamber, but instead providing heater blocks and bringing theheater blocks into direct contact with the devices under test to impartthermal stress for a burn-in test.

In such a burn-in system, since a burn-in test is conducted over a longperiod of time from several hours to several tens of hours, the testefficiency is raised by conducting the burn-in test simultaneously for alarge number of electronic devices. At this time, the test is desirablyperformed in a state giving as uniform a thermal stress as possible tothe large number of devices under test.

However, in actuality, even with the same lot of electronic devices,inherent defects, manufacturing variations, etc. result in eachelectronic device differing in consumed power, so the electronic devicessometimes vary in amounts of self generated heat as well. Therefore,even if simply heating the air in the burn-in chamber or bringing heaterblocks into contact with the devices, it is sometimes difficult to applya uniform thermal stress to the simultaneously tested plurality ofelectronic devices.

In particular, recent IC chips have become larger in capacity, higher inperformance, and faster in speed. Along with this, the amount of selfgenerated heat has been increasing as a general trend. Along with this,the variation in amount of self generated heat has also become larger asa general trend. Therefore, accurate control of the temperature of eachelectronic device in a burn-in test is being demanded.

SUMMARY OF THE INVENTION

The present invention has as its object the provision of a burn-insystem enabling the temperature of a large number of electronic devicesdiffering in amount of self generated heat to be simultaneously reliablyadjusted to a predetermined temperature.

To achieve this object, according to a first aspect of the presentinvention, there is provided a burn-in system bringing heating blockshaving heating means for heating a plurality of devices under testmounted on a burn-in board and cooling blocks formed with channels ableto carry a coolant for cooling the devices under test into contact withthe devices under test and simultaneously conducting a burn-in test onthe plurality of devices under test, wherein each cooling block isformed with a first accommodating space for accommodating the heatingblock, and each heating block is accommodated in a first accommodatingspace in a state with a layer of air formed with the cooling block so asto be insulated from the cooling block.

In the present invention, there is provided a burn-in system adjustingthe temperatures of a plurality of devices under test mounting on aburn-in board by heating blocks and cooling blocks and simultaneouslyperforming a burn-in test of those devices under test, wherein eachcooling block is formed with a first accommodating space andaccommodates the heating block in that first accommodating space in astate maintaining clearance.

Due to this, a layer of air is formed between each cooling device forcooling a device under test and the heating block for heating thatdevice under test, the heating block is insulated from the coolingblock, and the heating block is made thermally floating in state withrespect to the cooling block, so heat is not directly conducted from theheating block to the cooling block. For this reason, the heating meansof each heating block can positively and easily raise the temperature ofthe individual electronic device and coolant flowing through thechannels formed in each cooling block can be used to positively andeasily cool the individual electronic device, so when simultaneouslyperforming a burn-in test on a plurality of electronic devices, it ispossible to independently and accurately control the temperatures of theindividual electronic devices.

While not particularly limited in the present invention, preferably eachheating block is supported with play with respect to the cooling block,and when a heating block is not in contact with a device under test, afront end face of the heating block sticks out relative to a front endface of the cooling block.

By making the front end face of the heating block stick out from thefront end face of the cooling block, when contacting a device undertest, the heating block contacts the device under test before thecooling block. Further, as explained above, each heating block issupported with play with respect to the cooling block in a statemaintaining clearance between the heating block and the inside wallsurfaces of the first accommodating space, that is, the heating block isin a mechanically floating state with respect to the cooling block, sothe heating block contacting the device under test before the coolingblock operates fit against that device under test. Due to this, sincethe front end face of the heating block is in close contact with thedevice under test, the device under test can be efficiently raised intemperature.

While not particularly limited in the present invention, preferably eachheating block and cooling block have provided between them first biasingmeans for biasing the heating block to a front end side.

By providing first biasing means between each heating block and coolingblock, when the heating block contacts a device under test, that heatingblock is suitably pushed against and closely contacts the device undertest, so the device under test can be raised in temperature moreefficiently.

While not particularly limited in the present invention, preferably whena heating block is not in contact with the device under test, the firstbiasing means cause the heating block to be biased to a contact surfaceside and cause part of the heating block to contact the cooling block.

Due to this, the heat of the heating means of the heating block can beutilized to raise the temperature of the coolant flowing through thechannels of the cooling block, so there is no longer a need toseparately provide a heater for heating the coolant separate from thatheating means.

While not particularly limited in the present invention, preferably thesystem is further provided with measurement blocks having measuringmeans for measuring temperatures of the devices under test, each coolingblock is formed with a second accommodating space for accommodating themeasurement block, and each measurement block is accommodated in thesecond accommodating space in the state with a layer of air formed withthe cooling block so as to be insulated from the cooling block.

Due to this, a layer of air is formed between each cooling block forcooling a device under test and the measurement block for measuring thetemperature of the device under test, the measurement block is insulatedfrom the cooling block, and the measurement block is made thermallyfloating in state with respect to the cooling block, so the temperatureof the device under test can be accurately measured and the precision oftemperature adjustment is improved.

To achieve the object, according to a second aspect of the invention,there is provided a burn-in system bringing cooling blocks formed withchannels able to carry a coolant for cooling a plurality of devicesunder test mounted on a burn-in board and measurement blocks havingmeasuring means for measuring the temperatures of the devices under testinto contact with the plurality of devices under test and simultaneouslyconducting a burn-in test on the plurality of devices under test,wherein the system is further provided with variable flow rate means forvarying the flow rate of the coolant flowing through the channels formedin the cooling blocks, each cooling block is formed with a secondaccommodating space for accommodating the measurement block, and eachmeasurement block is accommodated in the second accommodating space in astate with a layer of air formed with the cooling block so as to beinsulated from the cooling block.

In the present invention, there is provided a burn-in system adjustingthe temperatures of a plurality of devices under test mounted on aburn-in board by cooling blocks and simultaneously performing a burn-intest on those devices under test, wherein the system is further providedwith variable flow rate means for varying the flow rates of coolantflowing through channels formed in the cooling blocks, each coolingblock is formed with a second accommodating space, and a measurementblock is accommodated in this second accommodating space in a statemaintaining clearance.

Due to this, without providing a heater or other heating means, eachvariable flow rate means can vary the flow rate of the coolant to adjustthe cooling thermal resistance of the cooling block and therefore thetemperature of each device under test can be easily adjusted, so whensimultaneously performing a burn-in test on a plurality of electronicdevices, it is possible to independently and accurately control thetemperature of each electronic device.

Further, a layer of air is formed between each cooling block for coolinga device under test and a measurement block for measuring thetemperature of the device under test, the measurement block is insulatedfrom the cooling block, and the measurement block is made thermallyfloating in state with respect to the cooling block, so the temperatureof the device under test can be accurately measured and the precision oftemperature adjustment is improved.

Further, to achieve the object, according to a third aspect of thepresent invention, there is provided a burn-in system provided with atleast cooling blocks formed with channels able to carry a coolant forcooling a plurality of devices under test mounted on a burn-in board andformed with openings communicating with the channels at their front endfaces, measurement blocks having measuring means for measuringtemperatures of the devices under test, variable flow rate means forvarying flow rates of the coolant through channels formed in the coolingblocks, and coolant recovering means for recovering coolant flowingthrough the channels, each cooling block formed with a secondaccommodating space for accommodating a measurement block, eachmeasurement block accommodated in a second accommodating space in astate with a layer of air formed with the cooling block so as to beinsulated from the cooling block, and pushing against the devices undertest mounted on the burn-in board the cooling blocks and the measurementblocks to bring the coolant into direct contact with the devices undertest through the openings and simultaneously conducting a burn-in teston the plurality of devices under test and, when the burn-in test ends,using the coolant recovering means to recover the coolant.

In the present invention, there is provided a burn-in system adjustingthe temperatures of a plurality of devices under test mounted on aburn-in board and simultaneously performing a burn-in test on thedevices under test, wherein the system is further provided with variableflow rate means for varying the flow rates of coolant flowing throughchannels formed in the cooling blocks and the front end faces of thecooling blocks are formed with openings communicating with the channels.Further, when pushing a cooling block against an electronic device, thecoolant supplied through the opening is made to directly contact thesurface of the device under test so as to cool the device under testwhen performing the burn-in test. After the burn-in test, the coolantrecovering means recovers the coolant from the surface of the deviceunder test.

Due to this, without providing a heater or other heating means, eachvariable flow rate means can vary the flow rate of the coolant to adjustthe temperature of the individual device under test directly and easily,so when simultaneously performing a burn-in test on a plurality ofelectronic devices, it is possible to independently and accuratelycontrol the temperature of each electronic device.

While not particularly limited in the invention, preferably eachmeasurement block is supported with play with respect to the coolingblock, and in the state where a measurement block is not in contact withthe device under test, the front end face of the measurement blocksticks out relative to the front end face of the cooling block.

By making the front end face of each measurement block stick out fromthe front end face of the cooling block, when contacting a device undertest, the measurement block contacts the device under test before themeasurement block. Further, as explained above, since each measurementblock is supported with play with respect to the cooling block in astate with a clearance maintained between the measurement block and theinside wall surface of the second accommodating space, that is, themeasurement block is in a mechanical floating state with respect to thecooling block, the measurement block contacting the device under testbefore the cooling block operates fit against that device under test.Due to this, the front end face of the measurement block closelycontacts the device under test, so the temperature of the device undertest can be more accurately measured.

While not particularly limited in the invention, preferably eachmeasurement block and cooling block are provided between them withsecond biasing means for biasing the measurement block to the front endface side.

By providing second biasing means between the measurement block and thecooling block, when the measurement block contacts a device under test,that measurement block is suitably pushed against and closely contactsthe device under test, so the temperature of the device under test canbe more accurately measured.

While not particularly limited in the invention, preferably in a statewhere a measurement block is not in contact with the device under test,the second biasing means cause the measurement block to be biased to thefront end side and cause part of the measurement block to contact thecooling block.

By bringing part of the measurement block into contact with the coolingblock before contacting a device under test, it becomes possible tomonitor the temperature of the cooling block or the state of operationof the heating means of the heating block or to enable self-diagnosis ofthat measuring means.

While not particularly limited in the invention, preferably the systemis further provided with temperature adjustment boards supporting aplurality of the cooling blocks at frames with play and a burn-inchamber able to hold each burn-in board and having the temperatureadjustment boards, each temperature adjustment board being provided inthe burn-in chamber so that each cooling block faces a device under testmounted on the burn-in board.

By further providing temperature adjustment boards supporting aplurality of cooling blocks at a frame with play, the cooling blocks areset in a mechanically floating state with respect to the temperatureadjustment boards.

Due to this, the variations in height of inclination of the devicesunder test mounted on the burn-in board can be absorbed, so the coolingblocks can be made to closely contact the devices under test and thetemperature of the devices under test can be accurately adjusted.

While not particularly limited in the invention, preferably each coolingblock is supported on a frame through third biasing means biasing thecooling block toward a burn-in board facing it in the burn-in chamber.

By providing third biasing means between each cooling block and theframe, when a cooling block contacts a device under test, that coolingblock is suitably pushed against and closely contacts the device undertest, so the temperature of the device under test can be more accuratelyadjusted.

While not particularly limited in the invention, preferably at leastpart of the channels formed at the plurality of cooling blocks areconnected in series.

By connecting the channels in series in this way, compared with whenconnecting all of them in parallel, it is possible to keep down theincrease in the number of connection points of the pipes in thetemperature adjustment boards and possible to improve the reliability ofthe pipes.

While not particularly limited in the invention, preferably each coolingblock is provided with a bypass for making the coolant bypass thechannels.

By providing such a bypass in each cooling block, when adjusting thetemperature of a device under test with a relatively low powerconsumption and not that large an amount of self generated heat, theflow rate of the coolant flowing through the channels can be suitablysecured and the temperature of the device under test can be suitablyadjusted.

While not particularly limited in the invention, preferably eachvariable flow rate means is provided in a channel or a bypass. Further,while not particularly limited in the invention, preferably the systemis further provided with a chiller able to adjust the temperature andflow rate of the coolant.

While not particularly limited in the invention, preferably thetemperature adjustment boards have first cooling blocks formed with thebypasses and second cooling blocks not formed with the bypasses.

By providing the same temperature adjustment board with two differenttypes of cooling blocks with different cooling performances due to thepresence/absence of bypasses, a single burn-in system can handle DUTswith a wide range of amounts of self-generated heat.

While not particularly limited in the invention, preferably the burn-inchamber has a plurality of the temperature adjustment boards, onetemperature adjustment board among the plurality of temperatureadjustment boards has first cooling blocks formed with the bypasses andthe other temperature adjustment boards have second cooling blocks notformed with the bypasses. Due to this, a single burn-in system canhandle DUTs with a wide range of amounts of self-generated heat.

While not particularly limited in the invention, preferably eachtemperature adjustment board has at least two types of cooling blockshaving different thermal resistances between the coolant and the devicesunder test.

By providing each temperature adjustment board with at least two typesof cooling blocks with different thermal resistances between the coolantand the devices under test, a single burn-in system can handle DUTs witha wide range of amounts of self-generated heat.

While not particularly limited in the invention, preferably the burn-inchamber has a plurality of the temperature adjustment boards, and athermal resistance between the coolant and the devices under test incoolant blocks in one temperature adjustment board among the pluralityof temperature adjustment boards and a thermal resistance between thecoolant and the devices under test in coolant blocks of the othertemperature adjustment boards are different. Due to this, a singleburn-in system can handle DUTs with a wide range of amounts ofself-generated heat.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clearer from the following description of the preferredembodiments given with reference to the attached drawings, wherein:

FIG. 1 is a front view of an overall burn-in system according to a firstembodiment of the present invention;

FIG. 2 is a side view of the overall burn-in system shown in FIG. 1;

FIG. 3 is a conceptual view of the system configuration of the burn-insystem shown in FIG. 1;

FIG. 4 is a plan view of an overall burn-in board mounting DUTs in thefirst embodiment of the present invention;

FIG. 5 is a plan view of a temperature adjustment board used in aburn-in system according to the first embodiment of the presentinvention;

FIG. 6 is a side view of a first temperature adjustment head supportedon the temperature adjustment board shown in FIG. 5;

FIG. 7 is a top plan view of the first temperature adjustment head shownin FIG. 6;

FIG. 8 is a bottom plan view of the first temperature adjustment headshown in FIG. 6;

FIG. 9 is a cross-sectional view of the first temperature adjustmenthead along the line IX-IX of FIG. 8;

FIG. 10 is a cross-sectional view of the first temperature adjustmenthead along the line X-X of FIG. 8;

FIG. 11 is a heat conduction model of a temperature adjustment head inthe first embodiment of the present invention;

FIG. 12 is a graph of the adjustable range of temperature of first tothird temperature adjustment heads in a burn-in system according to thefirst embodiment of the present invention;

FIG. 13 is a view of the state of temperature adjustment of a DUT by afirst temperature adjustment head in the first embodiment of the presentinvention;

FIG. 14 is a side view of a second temperature adjustment head used in aburn-in system according to the first embodiment of the presentinvention;

FIG. 15 is a bottom plan view of the second temperature adjustment headshown in FIG. 14;

FIG. 16 is a view of the state of temperature adjustment of a DUT by asecond temperature adjustment head in the first embodiment of thepresent invention;

FIG. 17 is a side view of a temperature adjustment head in a secondembodiment of the present invention;

FIG. 18 is a side view of a temperature adjustment head in a thirdembodiment of the present invention;

FIG. 19 is a bottom plan view of the temperature adjustment head shownin FIG. 18; and

FIG. 20 is a schematic view of a coolant recovering means of a burn-insystem according to a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, embodiments of the present invention will be explained based onthe drawings.

First Embodiment

FIG. 1 is a front view of an overall burn-in system according to a firstembodiment of the present invention, FIG. 2 is a side view of theoverall burn-in system shown in FIG. 1, FIG. 3 is a conceptual view ofthe system configuration of the burn-in system shown in FIG. 1, and FIG.4 is a plan view of an overall burn-in board mounting DUTs in the firstembodiment of the present invention.

First, explaining the overall configuration of the burn-in system 1according to the first embodiment of the present invention, this burn-insystem 1, as shown in FIG. 1 to FIG. 3, is provided with a burn-inchamber 100 which can hold burn-in boards 200 on which for example DUTs(devices under test) such as IC chips (corresponding to “device undertest” in the claims) are mounted and has temperature adjustment boards300 with temperature adjustment heads 400 for adjusting the DUTs intemperature arranged facing the burn-in boards 200; a DUT power source600 for supplying the DUTs with power voltage; a heater power source 700for driving heaters of the temperature adjustment heads 400 of thetemperature adjustment boards 300; a burn-in controller 800 forcontrolling the DUTs in temperature and controlling the supply of thepower voltage or signals etc.; and a chiller 900 for supplying a coolantto the temperature adjustment heads 400 of the temperature adjustmentboard 300.

This burn-in system 1 is a monitored burn-in system which pushes thetemperature adjustment heads 400 of the temperature adjustment boards300 against the DUTs, uses heaters and coolants to adjust the DUTs intemperature and apply thermal stress, and supplies power voltage andsupplies the input circuits of the DUTs with signals close to those ofactual operation for screening and for monitoring of the characteristicsof the output circuits of the DUTs.

Further, this burn-in system 1, for example, can simultaneously conductburn-in tests on 640 DUTs with different amounts of self-generated heatsuch as 0 to 100 W level medium heat emitting types, 100 to 200 W levelhigh heat emitting types, or, 200 to 300 W level superhigh heat emittingtypes.

The burn-in chamber 100 of the burn-in system 1 according to the presentembodiment, as shown in FIG. 1 and FIG. 2, has an inside chamber definedby heat insulating walls etc. and a door able to be opened and closedfor loading and unloading burn-in boards to and from the inside chamber.Further, the inside chamber of this burn-in chamber 100 is provided with16 levels and two rows of slots 110 for supporting the burn-in boards200 and therefore can hold a total of 32 burn-in boards 200. Note thatthe number and arrangement of the slots 110 in this burn-in chamber 100are not particularly limited in the present invention and can be freelyset in consideration of the test efficiency etc.

Further, as shown in FIG. 2, the back of each slot 110 is provided witha connector 120 into which an edge connector 202 of a burn-in board 200(see FIGS. 3 and 4) can be inserted. This connector 120, as shown inFIG. 3, is electrically connected to the DUT power source 600 and theburn-in controller 800. Note that FIG. 3 only illustrates one set of theburn-in board 200 and temperature adjustment board 300, but the other 31sets of burn-in boards 200 and temperature adjustment boards 300 aresimilarly connected to the DUT power source 600, heater power source700, burn-in controller 800, and, chiller 900. Further, the air in theburn-in chamber 100 is circulated by a fan (not shown) etc. so as tokeep heated air around the DUTs from stagnating there, but is notcontrolled to the extent of adjusting the DUTs in temperature.

Here, a burn-in board 200 held in the burn-in chamber 100 will beexplained. This burn-in board 200, as shown in FIG. 4, is comprised of20 burn-in sockets 201 able to mount DUTs arranged on a board withsuperior heat resistance in four rows and five columns. One side edge ofthat board is formed with an edge connector 202 able to be inserted intoa connector 120 formed in the burn-in chamber 100. Note that the numberand arrangement of the burn-in sockets 201 on the burn-in board 200 arenot particularly limited in the present invention and can be freely setin consideration of the test efficiency etc.

That board is further formed with a printed circuit (not shown)electrically connecting this edge connector 202 and the burn-in sockets201. When the edge connector 202 of the burn-in board 200 is insertedinto the connector 120 of the burn-in chamber 100, the DUTs mounted onthe burn-in board 200 are electrically connected to the DUT power source600 and the burn-in controller 800 through this printed circuit and theburn-in sockets 201. Note that while not particularly illustrated, thework for insertion and removal of DUTs to and from the burn-in sockets201 of this burn-in board 200 is performed for example outside of theburn-in system 1 using an inserter/remover, loader/unloader, etc.

The burn-in chamber 100, as shown in FIG. 1 to FIG. 3, further isprovided with 32 temperature adjustment boards 300 for adjusting theDUTs in temperature arranged so as to face the burn-in boards 200supported at the slots 110. Each temperature adjustment board 300 isable to be raised and lowered in the vertical direction by air cylinders130 (see FIG. 3) under the control of the burn-in controller 800 sothat, at the time of a burn-in test, the temperature adjustment heads400 can be brought into contact with the DUTs and, at the time ofnon-contact, the temperature adjustment heads 400 can be moved away fromthe DUTs. Note that temperature adjustment board 300 will be explainedlater in detail.

The DUT power source 600 of the burn-in system 1 according to thepresent embodiment, as shown in FIG. 3, is connected to the DUTs throughthe connectors 120 of the burn-in chamber 100 and the edge connectors202, printed circuits, and burn-in sockets 201 of the burn-in boards 200to be able to supply power voltage to the DUTs and is controlled by theburn-in controller 800. Further, the heater power source 700, as shownin FIG. 3, is connected so as to be able to supply power to the heaters(explained later) provided at the temperature adjustment boards 300 inthe burn-in chamber 100 and is controlled by the burn-in controller 800.

The burn-in controller 800 of the burn-in system 1 according to thepresent embodiment controls the temperatures of the DUTs during theburn-in test, the voltages supplied to the DUTs, and the signalssupplied to them. In addition, it judges any DUT exhibiting abnormalreactions during the burn-in tests to be defective, for example, holdsthe serial number of the DUT linked with the number of the slot in theburn-in chamber 100 and the position on the burn-in board 200, and feedsback the test results.

This burn-in controller 800, as shown in FIG. 3, is connected totemperature sensors (explained later) provided at the temperatureadjustment boards 300 in the burn-in chamber 100 so as to enabledetection of the temperatures of the DUTs and is connected to the heaterpower source 600 and chiller 900 so as to enable control of thetemperatures of the DUTs. Further, it is connected to the DUT powersource 700 so as to enable control of the power voltage supplied to theDUTs.

These DUT power source 600, heater power source 700, and burn-incontroller 800 are held in an instrument rack 500 shown in FIG. 1.

The chiller 900 of the burn-in system 1 according to the presentembodiment causes a fluorine-based inert liquid (for example, 3MFluorinert FC-323) or other coolant to circulate to the cooling blocks(explained later) of the temperature adjustment board 300 in the burn-inchamber 100 and can adjust the coolant in temperature and flow rateunder the control of the burn-in controller 800. Note that the coolantin the present invention is not limited to the above liquid and forexample may also be a gas.

Below, a temperature adjustment board 300 used in the burn-in system 1according to the present embodiment will be explained.

FIG. 5 is a plan view of a temperature adjustment board used in aburn-in system according to the first embodiment of the presentinvention, FIG. 6 is a side view of a first temperature adjustment headsupported on the temperature adjustment board shown in FIG. 5, FIG. 7 isa top plan view of the first temperature adjustment head shown in FIG.6, FIG. 8 is a bottom plan view of the first temperature adjustment headshown in FIG. 6, FIG. 9 is a cross-sectional view of the firsttemperature adjustment head along the line IX-IX of FIG. 8, FIG. 10 is across-sectional view of the first temperature adjustment head along theline X-X of FIG. 8, FIG. 11 is a heat conduction model of a temperatureadjustment head in the first embodiment of the present invention, FIG.12 is a graph of the adjustable range of temperature of first to thirdtemperature adjustment heads in a burn-in system according to the firstembodiment of the present invention, FIG. 13 is a view of the state oftemperature adjustment of a DUT by a first temperature adjustment headin the first embodiment of the present invention, FIG. 14 is a side viewof a second temperature adjustment head used in a burn-in systemaccording to the first embodiment of the present invention, FIG. 15 is abottom plan view of the second temperature adjustment head shown in FIG.14, and FIG. 16 is a view of the state of temperature adjustment of aDUT by a second temperature adjustment head in the first embodiment ofthe present invention.

The temperature adjustment board 300 of the present embodiment, as shownin FIG. 5 and FIG. 6, is provided with 20 temperature adjustment heads400 for adjusting the DUTs in temperature, a frame 301 for supportingthe temperature adjustment head 400 s, and main pipes 302 and branchpipes 303 for supplying the cooling blocks of the temperature adjustmentheads 400 with coolant from the chiller 900.

The frame 301 of this temperature adjustment board 300, as shown in FIG.5, is a flat plate member formed with four rows and five columns, or atotal of 20, openings 3011 corresponding to the arrangement of the DUTsmounted on a burn-in board 200 (arrangement of burn-in sockets 201).Further, as shown in FIG. 6, each opening 3011 has a temperatureadjustment head 400 inserted into it. As shown in FIG. 9 and FIG. 10,each temperature adjustment head 400 is supported with play with respectto the frame 301 by supporting parts 304 of the frame 301 via thirdsprings 305 (third biasing means) pressing that temperature adjustmenthead 400 to the facing burn-in board 200 side.

By setting each of the temperature adjustment heads 400 in a mechanicalfloating state with respect to the temperature adjustment board 300 inthis way, variations in height or inclination of the DUTs mounted on theburn-in board 200 can be absorbed by the temperature adjustment heads400.

Further, by having each of the temperature adjustment heads 400supported by the frame 301 via third springs 305 pushing the temperatureadjustment heads 400 to the burn-in board 200 side, when eachtemperature adjustment head 400 contacts a DUT, that temperatureadjustment head 400 can be made to be suitably pushed against andclosely contact the DUT.

The temperature adjustment head 400 in the first embodiment of thepresent invention includes a first temperature adjustment head 400 a forexample for 0 to 100 W level medium heat emitting types of DUTs, asecond temperature adjustment head 400 b for example for 100 to 200 Wlevel high heat emitting types of DUTs, and a third temperatureadjustment head for example for 200 to 300 W level superhigh heatemitting types of DUTs. By selecting the suitable type from among thetotal three types of temperature adjustment heads by considering theamount of self generated heat of the DUTs in question, it becomespossible to handle DUTs of a broad range of amount of self generatedheat by a single burn-in system 1 (see FIG. 12). Note that the secondand third temperature adjustment heads will be explained in detaillater, but no matter which temperature adjustment heads are employed,the temperature adjustment board 300 is configured the same except forthe temperature adjustment heads.

Each first temperature adjustment head 400, as shown in FIG. 6, isprovided with a cooling block 410 a for cooling a DUT, a heater block420 a for heating a DUT, and a sensor block 430 a for measuring thetemperature of a DUT.

The cooling block 410 a of this first temperature adjustment head 400 ais made of aluminum, copper, or another material superior in heatconductivity. As shown in FIG. 6 and FIG. 7, this cooling block 410 a isformed inside it with an inside space 412 a for circulation of thecoolant supplied from the chiller 900. Further, this cooling block 410 ais formed inside it with an entrance side channel 41 a connecting abranch pipe 303 and the inside space 412 a so as to extend downward atan angle along the direction of progression of the coolant and is formedinside it with an exit side channel 413 a connecting the inside space412 a and a branch pipe 303 so as to extend upward at an angle along thedirection of progression of the coolant. The flow of the coolant isutilized for circulating it through the inside space 412 a.

Further, in this first temperature adjustment head 400 a, the coolantsupplied from the chiller 900 through a main pipe 302 and branch pipe303 to a cooling block 410 a flows from the branch pipe 303 through theentrance side channel 411 a to the inside space 412 a so can cool theDUT contacting that cooling block 410 a.

Further, between the entrance side channel 411 a and the exit sidechannel 413 a, a bypass 414 a is formed branching off from the entranceside channel 411 a and the exit side channel 413 a to make the coolantbypass the inside space 412 a.

The medium heat emitting type of DUT covered by this first temperatureadjustment head 400 a has a relatively low amount of self generated heatcompared with the above-mentioned high heat emitting or superhigh heatemitting type of DUT, so if circulating a similar amount of coolant aswith the second and third temperature adjustment heads for other typesof DUTs through the inside space 412 a, the head will be overcooled andmay not be able to impart the predetermined thermal stress to the DUT.As opposed to this, in the first temperature adjustment head 400 a ofthe present embodiment, the excess flow of coolant is made to bypass thespace by the bypass 414 a so as to limit the flow of coolant passingthrough the inside space 412 a. Due to this, when adjusting thetemperature of a DUT with a relatively low amount of self generatedheat, it is possible to make the flow of the coolant through the insidespace suitable and possible to suitably adjust the DUT in temperature.

This cooling block 410 a is formed with a first accommodating space 415a for accommodating the heater block 420 a and a second accommodatingspace 416 a for accommodating the sensor block 430 a.

This first accommodating space 415 a, as shown in FIG. 6, FIG. 8, andFIG. 9, has a size enabling a predetermined clearance to be securedbetween the heater block 420 a and the inside wall surfaces of thatfirst accommodating space 415 a. Further, this first accommodating space415 a is formed to open at the surface of the cooling block 410 acontacting the DUT.

Further, the second accommodating space 416 a similarly, as shown inFIG. 6, FIG. 8, and FIG. 10, has a size enabling a predeterminedclearance to be secured between the sensor block 430 a and the insidewall surfaces of that second holding space 416 b. Further, this secondholding space 416 a is formed to open at the surface of the coolingblock 410 a contacting the DUT.

The heater block 420 a of the first temperature adjustment head 400 a,like the cooling block 410 a, is comprised of aluminum, copper, oranother material superior in heat conductivity. As shown in FIG. 9, ithas a substantially projecting shape overall, is formed at its front endwith a projecting part 422 a projecting outward, and has for example a100 W level heat generating heater 421 a embedded inside it. This heater421 a, as shown in FIG. 3, is connected to the heater power source 700so as to be able to be supplied with power from it.

This heater block 420 a, as shown in FIG. 6 and FIG. 8, is accommodatedin the first accommodating space 415 a in a state with a clearancemaintained from the inside wall surfaces of the first accommodatingspace 415 a of the cooling block 410 a.

Therefore, this heater block 420 a is accommodated in a statemaintaining clearance from the first accommodating space 415 a, a layerof air is formed between the heater block 420 a and the cooling block410 a, the cooling block 410 a is insulated from the heater block 420 a,and the heater block 420 a is in a thermally floating state with respectto the cooling block 410 a, so heat will not be directly conducted fromthe heater block 420 a to the cooling block 410 a.

This heater block 420 a, as shown in FIG. 9, is supported at its top twoends through first springs 423 a (first biasing means) with respect tothe cooling block 410 a and is pushed in the downward direction in thefigure by the first springs 423 a. Due to this, when the heater block420 a is not in contact with the DUT, the heater block 420 a is pushedby the first springs 423 a so that the shoulders 424 of the heater block420 a contact the cooling block 410 a. Further, the pushing action ofthe first springs 423 a causes the front end face of the projecting part422 a to stick out relative to the front end face of the cooling block410 a.

By making the front end face of the projecting part 422 a of the heaterblock 420 a stick out relative to the front end face of the coolingblock 410 a in this way, when contacting the DUT, the heater block 420contacts it earlier than the cooling block 410 a. Further, the heaterblock 420 a is supported with play with respect to the cooling block 410a in a state securing clearance from the inside wall surfaces of thefirst accommodating space 415 a, that is, the heater block 420 a is in amechanically floating state with respect to the cooling block 410 a, sothe heater block 420 a contacting the DUT earlier than the cooling block410 a can operate fit against the DUT.

Further, by providing the first springs 423 a between the heater block420 a and the cooling block 410 a so as to push the heater block 420 ato the DUT side, when the heater block 420 a contacts the DUT, thatheater block 420 a can be made to be suitably pushed against and closelycontact the DUT.

The sensor block 430 a of the first temperature adjustment head 400 a,like the cooling block 410 a, is comprised of aluminum, copper, oranother material superior in heat conductivity. As shown in FIG. 10, ithas a substantially projecting shape overall, is formed at its front endwith a projecting part 432 a projecting outward, and has for example aplatinum sensor or other temperature sensor 431 a embedded inside it.This temperature sensor 431 a, as shown in FIG. 3, is connected to theabove-mentioned burn-in controller 800 so as to be able to transmit thedetected temperature of the DUT to it.

This sensor block 430 a, as shown in FIG. 6 and FIG. 8, is accommodatedin the second accommodating space 416 a in a state maintaining clearancewith the inside wall surfaces of the second accommodating space 416 a ofthe cooling block 410 a.

Therefore, this sensor block 430 a is accommodated in a statemaintaining clearance with respect to the second accommodating space 416a, a layer of air is formed between the sensor block 430 a and thecooling block 410 a, the sensor block 430 a is insulated from thecooling block 410 a, and the sensor block 430 a is in a thermallyfloating state with respect to the cooling block 410 a, so heat will notbe directly conducted from the cooling block 410 a to the sensor block430 a, and the temperature of the DUT can be accurately measured.

This sensor block 430 a, as shown in FIG. 10, is supported at its toptwo ends through second springs 433 a (second biasing means) withrespect to the cooling block 410 a and is pushed in the downwarddirection in the figure by the second springs 433 a. Due to this, whenthe sensor block 430 a is not in contact with the DUT, the sensor block430 a is pushed by the second springs 433 a so that the shoulders 434 ofthe sensor block 430 a contact the cooling block 410 a. Further, thepushing action of the second springs 433 a causes the front end face ofthe projecting part 433 a to stick out relative to the front end face ofthe cooling block 410 a.

By making the front end face of the projecting part 432 a of the sensorblock 430 stick out relative to the front end face of the cooling block410 a in this way, when contacting the DUT, the sensor block 430 acontacts it earlier than the cooling block 410 a. Further, the sensorblock 430 a is supported with play with respect to the cooling block 410a in a state securing clearance from the inside wall surfaces of thesecond accommodating space 416 a, that is, the sensor block 430 a is ina mechanically floating state with respect to the cooling block 410 a,so the sensor block 430 a contacting the DUT earlier than the coolingblock 410 a can operate fit against the DUT.

Further, by providing the second springs 433 a between the sensor block430 a and the cooling block 410 a so as to push the sensor block 430 ato the DUT side, when the sensor block 423 a contacts the DUT, thatsensor block 430 a can be made to be suitably pushed against and closelycontact the DUT.

The first temperature adjustment head 400 a configured in this way canbe expressed by a heat conduction model such as shown in FIG. 11 sincethe heater block 420 a is thermally floating with respect to the coolingblock 410 a. When the amount of heat generated by a DUT is Hd [W], thetemperature of the coolant is Tw [° C.], the amount of heat generated bythe heater 421 a is Hh [W], and the thermal resistance between the DUTand coolant is θ [° C./W], the temperature Tc [° C.] of the DUT isexpressed by Tc=Tw+θcw(Hh+Hd). From this heat conduction model andequation as well, it is learned that the flow of heat from the heaterblock 420 a having the heater 421 a to the surrounding air is extremelysmall and that the majority of the heat generated at the heater block420 a flows to the DUT, so the heater block 420 a can positively raisethe temperature of the DUT.

Note that the thermal resistance θ cw spoken of here is comprised of thecontact thermal resistance at the contact part of the cooling block 410a and DUT surface, the thermal resistance of that cooling block 410 aitself, and the coolant thermal resistance based on the heat conductionarea of the coolant, etc.

Note that in the first temperature adjustment head 400 a in thisembodiment, as shown in FIG. 12, when the coolant temperature can bechanged in a range of 27° C.≦Tw≦80° C., by setting the thermalresistance θ cw to 0.6° C./W, it is possible to adjust the temperatureTc of a DUT varying in amount of self generated heat in the range of 0 Wto 100 W by the heater 421 a and set the DUT temperature to the range ofabout 87° C. to about 140° C.

Four rows and five columns of such first temperature adjustment heads400 a, as shown in FIG. 5, are supported by the frame 301. This frame301 is provided with main pipes 302 and branch pipes 303 for supplyingcoolant from the chiller 900 to the first temperature adjustment heads400 a. One main pipe 302 splits into five parallel branch pipes 303.Each branch pipe 303 serially connects the inside spaces 412 a of thefour heads 400 a arranged in the same line in the frame 301. Note thatwhile not particularly shown, the pressure of the coolant is adjusted byorifices etc. so that the pressures of the coolant at the firsttemperature adjustment heads 400 a become substantially uniform.

By serially connecting the inside spaces 412 a of the first temperatureadjustment heads 400 a in this way, compared with when connecting alltemperature adjustment heads in parallel, it is possible to keep downthe increase in the number of connection points of the pipes at thetemperature adjustment board 300 and possible to improve the reliabilityof the pipes.

Next, the action of the burn-in system 1 using this first temperatureadjustment head 400 a will be explained.

Each slot 110 of the burn-in chamber 100 holds a burn-in board 200mounting DUTs. An edge connector 202 of each burn-in board 200 isinserted into a connector 120 of the burn-in chamber 100. When the doorof the burn-in chamber 100 is closed and a start button (not shown) ispushed etc. to start the burn-in test, first the air cylinders 130 aredriven to descend based on a control signal from the burn-in controller800, each temperature adjustment board 300 in the burn-in chamber 100descends with respect to the burn-in board 200 held in the slot 110, andfirst temperature adjustment heads 400 a arranged on that temperatureadjustment board 300 contact the DUTs arranged on the burn-in board 200.

At the time of this contact, the front end face of the projecting part422 a of each heater block 420 a sticks out relative to the front endface of the cooling block 410 a, so the heater block 420 a contacts thedevice under test before the cooling block 410 a. Further, each heaterblock 420 a is in a mechanically floating state with respect to thecooling block 410 a, so the heater block 420 a contacting the DUT beforethe cooling block 410 a operates fit against the DUT and the front endface of the heater block 420 a closely contacts the DUT, so the DUT canbe efficiently raised in temperature.

Further, by providing pushing the heater block 420 a to the DUT sidebetween each heater block 420 a and cooling block 410 a first springs423 a, when a first temperature adjustment head 400 a contacts a DUT,that heater block 420 a is suitably pushed against and closely contactsthe DUT, so the DUT can be more efficiently raised in temperature.

Similarly, since the front end face of the projecting part 432 a of eachsensor block 430 a sticks out relative to the front end face of thecooling block 410 a, when a first temperature adjustment head 400 acontacts a DUT, the sensor block 430 a contacts the DUT before thecooling block 410 a. Further, the sensor block 430 a is in amechanically floating state with respect to the cooling block 410 a, sothe sensor block 430 a contacting the DUT before the cooling block 410 aoperates fit against the DUT and the front end face of the sensor block430 a closely contacts the DUT, so the temperature of the DUT can bemore accurately measured.

Further, by providing second springs 433 a between each sensor block 430a and cooling block 410 a, when a first temperature adjustment head 400a contacts a DUT, that heater block 420 a is suitably pushed against andclosely contacts the DUT, so the temperature of the DUT can beaccurately measured.

Further, since each first temperature adjustment head 400 a is supportedwith play with respect to the temperature adjustment board 300, when afirst temperature adjustment head 400 a contacts a DUT, variations inheight or inclination of the DUT mounted on the burn-in board 200 can beabsorbed by the first temperature adjustment head 400 a, and the firsttemperature adjustment heads 400 a can be made to closely contact theDUT, so this first temperature adjustment head 400 a enables thetemperature of the DUT to be more accurately adjusted.

Further, by having each first temperature adjustment head 400 asupported on a frame 301 through third springs 305, when a firsttemperature adjustment head 400 a contacts a DUT, it is possible to makethat first temperature adjustment head 400 a be suitably pushed againstand closely contact the DUT, so this first temperature adjustment head400 a enables the temperature of the DUT to be more accurately adjusted.

Note that up until right before a first temperature adjustment head 400a contacts a DUT, the shoulders 424 of the heater block 420 a contactthe cooling block 410 a due to the action of the first springs 423 a.Due to this, the heater 421 a of the heater block 420 a can be used toraise the temperature of the coolant flowing through the channels of thecooling block 410 a, so there is no longer a need to provide the chiller900 with a heater etc. for heating the coolant.

Similarly, up until right before the first temperature adjustment head400 a contacts a DUT, the shoulders 434 of the sensor block 430 acontact the cooling block 410 due to the action of the second springs433 a. Due to this, the temperature of the cooling block 410 a or theoperating state of the heater 421 a of the heater block 420 a can bemonitored or the temperature sensor 431 a itself can be diagnosed.

As shown in FIG. 13, when a first temperature adjustment head 400 acontacts a DUT, the burn-in controller 800 monitors the temperature ofthe DUT by the temperature sensor 431 a of the sensor block 430 a andheats the heater 321 a of the heater block 420 a so as to apply thermalstress to the DUT and raise it to a predetermined DUT temperature. ThisDUT temperature is for example 125° C.

When the temperature of the DUT reaches a predetermined temperature, theburn-in controller 800 supplies that DUT with power voltage and a signalclose to that of actual operation through the connector 120 of theburn-in chamber 200 and the edge connector 202 of the burn-in board 200for screening. Due to the supply of this power voltage, the DUTgenerates heat by itself and so the DUT changes in temperature, so thetemperature sensor 431 a is used to monitor the DUT for temperature andthe heater 421 a is turned on/off so as to adjust the temperature of theDUT to a predetermined temperature.

When applying this thermal stress, since each heater block 420 a is in athermally floating state with respect to the cooling block 410 a, heatis not directly conducted from the heater block 420 a to the coolingblock 410 a, the heater block 420 a can be used to positively raise thetemperature of the individual DUT, the cooling block 410 a can be usedto positively cool that DUT, when simultaneously performing a burn-intest on a plurality of electronic devices, it is possible toindependently and accurately control the temperature of each DUT.

Further, when applying this thermal stress, since each sensor block 430a is in a thermally floating state with respect to the cooling block 410a, heat is not directly conducted from the cooling block 410 a to thesensor block 430 a, the temperature of the individual DUT can beaccurately measured, and the precision of temperature adjustment of theDUT is improved.

The above burn-in test is performed continuously over a long period ofseveral hours to tens of hours. During that burn-in test, any DUTexhibiting an abnormal reaction is judged defective. For example, theserial number of that DUT can be held in the burn-in controller 800 andthe test results fed back.

Next, for example, a second temperature adjustment head 400 b fordealing with 100 to 200 W level high heat emitting types of DUTs will beexplained.

This second temperature adjustment head 400 b, as shown in FIG. 14 toFIG. 16, is provided with a cooling block 410 b for cooling a DUT, aheater block 420 b for heating a DUT, and a sensor block 430 b formeasuring a DUT for temperature. Aside from a bypass for making thecoolant bypass the inside space not being formed in the cooling block,this is structured similar to the above-mentioned first temperatureadjustment head 400 a.

This second temperature adjustment head 400 b deals with relativelylarge heat emitting 100 to 200 W level high heat emitting types of DUTsand is required to exhibit a higher cooling performance compared withthe first temperature adjustment head 400 a, so as shown in that figureis not formed with a bypass like the abovementioned first temperatureadjustment head 400 a. The entire amount of the coolant supplied fromthe branch pipe 303 through the entrance side channel 411 b and exitside channel 413 b is designed to flow through the inside space 412 b.

Further, this second temperature adjustment head 400 b makes the thermalresistance θ cw between a DUT and the coolant 0.4° C./W and thereforelowers that thermal resistance θ cw more than the first temperatureadjustment head 400 b to improve the cooling efficiency. Note that asthe method for reducing the thermal resistance θ cw, for example, themethods of strengthening the pushing force of the temperature adjustmenthead, using a material more superior in heat conductivity to make thecooling block, increasing the heat conduction area of the coolant, etc.may be illustrated.

Due to this, as shown in FIG. 12, when the coolant may vary intemperature in the range of 27° C.≦T w≦80° C., the temperature Tc of aDUT, which may vary in amount of self generated heat in the range of 100W to 200 W, may be adjusted by the heater 421 b so as to set the DUTtemperature at any temperature in the range of about 107° C. to about160° C.

Next, for example, a third temperature adjustment head for dealing with200 to 300 W level superhigh heat emitting types of DUTs will beexplained.

This third temperature adjustment head, while not particularlyillustrated, is basically the same in configuration as the secondtemperature adjustment head 400 b. However, the third temperatureadjustment head deals with 200 W to 300 W level superhigh heat emittingtypes of DUTs, so is required to exhibit a higher cooling performancethan the second temperature adjustment head 400 b.

Therefore, this third temperature adjustment head makes the thermalresistance θ cw between a DUT and the coolant 0.28° C./W and reducesthat thermal resistance θ cw more than the second temperature adjustmenthead 400 c so as to further improve the cooling performance.

Due to this, as shown in FIG. 12, when the coolant may vary intemperature in the range of 27° C.≦T w≦80° C., the temperature Tc of theDUT, which may vary in amount of self generated heat in the range of 200W to 300 W, may be adjusted by a heater built in the heater block tofreely set the DUT temperature in the range of about 111° C. to about164° C.

Further, in the burn-in system 1 according to the present embodiment,among the total three types of temperature adjustment heads explainedabove changing the cooling performance by the presence/absence ofbypasses and changing the thermal resistance between the DUTs andcooling blocks, the one matching the amount of self generated heat ofeach DUT is selected to enable DUTs of a wide range of amounts of selfgenerated heated of 0 W to 300 W or so to be handled by the same burn-insystem.

Note that the first to third temperature adjustment heads may be mountedmixed on the same temperature adjustment board 300 or first temperatureadjustment heads 400 a may be mounted on one temperature adjustmentboard 300, second temperature adjustment heads 400 b mounted on anothertemperature adjustment board 300, and third temperature adjustment headsmounted on another temperature adjustment board 300.

Second Embodiment

FIG. 17 is a side view of a temperature adjustment head in a secondembodiment of the present invention.

The burn-in system according to the second embodiment of the presentinvention differs in structure of the temperature adjustment head fromthe burn-in system 1 according to the first embodiment, but the rest ofthe configuration is identical to that of the burn-in system 1 accordingto the first embodiment. Below, the burn-in system according to thesecond embodiment will be explained only with reference to the points ofdifference from the burn-in system 1 according to the first embodiment.

The temperature adjustment head 400′ in the present embodiment, as shownin FIG. 17, is not provided with any heater block. Instead, a bypass414′ of the cooling block 410′ is provided with a valve 417′ (variableflow rate means). The head differs from the first temperature adjustmenthead 400 a in the first embodiment on this point, but otherwise is thesame in configuration.

In the first temperature adjustment head 400 a in the first embodiment,the heater 421 a of each heater block 420 a was used to adjust a DUT intemperature, but in the temperature adjustment head 400′ in thisembodiment, instead of a heater, the valve 417′ is operated to adjustthe flow rate of the coolant flow through the inside space 412 a throughthe channels 411 a and 413 a to thereby adjust the DUT in temperature.

The valve 417′ provided at this temperature adjustment head 400′, whilenot particularly illustrated, is connected to the burn-in controller toenable control. Based on on/off signals of that burn-in controller, thevalve 417′ is operated to adjust the flow rate of coolant flowingthrough the bypass 414′. Note that this valve 417′ may also be providednot at the bypass 414′, but at the entrance side channel 411′ or exitside channel 413′.

As explained above, in the burn-in system according to the secondembodiment of the present invention, instead of the heater, a valve 417′is provided at the entrance side channel 411′ formed in the coolingblock 410′ of each temperature adjustment head 400′. This valve 417′ isused to change the flow rate of the coolant so as to adjust the coolingthermal resistance in the cooling block 410′. Due to this, theindividual DUTs can be easily adjusted in temperature, so whensimultaneously performing a burn-in test on a plurality of electronicdevices, it is possible to independently and accurately control thetemperatures of the individual DUTs.

Third Embodiment

FIG. 18 is a side view of a temperature adjustment head in a thirdembodiment of the present invention, FIG. 19 is a bottom plan view ofthe temperature adjustment head shown in FIG. 18, and FIG. 20 is aschematic view of a coolant recovering means of a burn-in systemaccording to a third embodiment of the present invention.

In the burn-in systems according to the first and second embodimentsexplained above, the DUTs were indirectly cooled by coolant through thecooling blocks so as to adjust the DUTs in temperature, but in theburn-in system according to the third embodiment of the presentinvention, the coolant is made to directly contact the DUTs to adjustthe DUTs in temperature.

Therefore, the burn-in system according to the third embodiment of thepresent invention differs in the structure of the temperature adjustmentheads. Further, it differs from the burn-in system 1 according to thefirst embodiment in the point of being provided with coolant recoveringmeans for recovering the coolant after the burn-in test, but rest of theconfiguration is identical to that of the burn-in system 1 according tofirst embodiment. Below, the burn-in system according to the thirdembodiment will be explained with reference to only the points ofdifference from the burn-in system 1 according to the first embodiment.

First, explaining the temperature adjustment head 400″ according to thisembodiment, this temperature adjustment head 400″, as shown in FIG. 18and FIG. 19, is similar to the second temperature adjustment head 400 baccording to the first embodiment (see FIG. 14 to FIG. 16), but differsfrom the second temperature adjustment head 400 b according to the firstembodiment in the point that the cooling block 410″ of this temperatureadjustment head 400″ does not have any part corresponding to the bottomhalf of the cooling block 410 b of that second temperature adjustmenthead 400 b and in the point that instead of a heater block, a valve 417″(variable flow rate means) is provided.

More specifically, the cooling block 410″ of each temperature adjustmenthead 400″ according to this embodiment is shaped as the cooling block410 b of the second temperature adjustment head 400 b cut off so thatits inside space 412 b is open. Due to this, the entrance side channel411″ communicating with the branch pipe 303 opens at the entrance sideopening 4111″ formed at the bottom end face of the cooling block 410″.Similarly, the exit side channel 413″ communicating with the branch pipe303 opens at an exit side opening 4131 formed at the bottom end face ofthe cooling block 410″.

Further, the cooling block 410″ of this temperature adjustment head 400″is formed with a second holding space 416″. A sensor block 430″ with abuilt-in temperature sensor 431″ is accommodated in that accommodatingspace 416″ in a state maintaining a clearance. Note that the temperatureadjustment head 400″ according to this embodiment, like the temperatureadjustment head 400′ according to the second embodiment, is not providedwith any heater block with a built-in heater.

Further, the bottom end face of this cooling block 410″ is fit with ringshaped packings 481″ at its outer periphery and at the periphery of theaccommodating space 416″ in which the sensor block 430″ is accommodated.

Therefore, when the temperature adjustment head 400″ according to thepresent embodiment contacts a DUT, as shown in FIG. 18, the bottom endface of that temperature adjustment head 400″, the packings 418″, andthe top face of the DUT define a space 419″. Coolant CL supplied throughthe entrance side opening 4111″ of the entrance side channel 411″ entersthis space 419″, so that coolant can directly contact the DUT.

Further, the temperature adjustment head 400″ according to the presentembodiment has a valve 417″ for adjusting the flow rate of the coolant.That valve 417″ is provided inside the entrance side channel 411″ formedat the cooling block 410″. Note that the mounting position of this valve417″ is not particularly limited in the present invention. For example,the valve may also be provided at the exit side channel.

The valve 417″ provided at this temperature adjustment head 400″, whilenot particularly limited, is connected to the burn-in controller forcontrol. Based on on/off control of that burn-in controller, the valve417″ is operated to adjust the flow rate of the coolant flowing throughthe entrance side channel 411″.

Next, explaining the coolant recovering means according to the burn-insystem according to the present embodiment, as shown in FIG. 20, thecoolant recovering means in this embodiment is provided at the chiller900″. This chiller 900″ is provided with a pump 901 for circulating thecoolant, a heat exchanger 902 for transferring the heat of the coolantto for example about 20° C. or less cooling water so as to cool thecoolant, a tank 903 for holding the recovered coolant, and a compressedgas supply apparatus 904 for recovering the coolant and can form acirculation route from the pump 901 through a temperature adjustmenthead 400″ (more specifically, the channels 411″ and 413″), tank 903, andheat exchanger 902 and back to the pump 901.

This circulation route is provided with two valves S1 and S2. The firstvalve S1 is provided between the pump 901 and the temperature adjustmenthead 400″, while the second valve S2 is provided between the temperatureadjustment head 400″ and the tank 903.

Further, this circulation route is connected through a third valve S3 tothe compressed gas supply apparatus 904. This compressed gas supplyapparatus 904 supplies compressed gas to the circulation route toforcibly recover coolant directly contacting the DUTs in the tank 903after the burn-in test. As the gas supplied from this compressed gassupply apparatus 904, for example, nitrogen gas may be mentioned.Further, along with the employment of recovery using this compressedgas, the pressure of the compressed gas is released into the atmosphereafter the coolant is recovered, so the tank 903 is provided with afourth valve S4. Note that the first to fourth valves S1 to S4 are all,while not particularly shown, connected to the burn-in controller forcontrol. Based on on/off control of that burn-in controller, the valvesS1 to S4 are operated.

Next, the method of recovery of the coolant recovering means provided atthis chiller 900″ will be explained.

First, when adjusting the temperatures of the DUTs in the burn-in test,the first and second valves S1 and S2 are opened, the third and fourthvalves S3 and S4 are closed, and a circulation route is formed.Therefore, in this state, the action of the pump 901 causes the coolantto circulate through the circulation route. The coolant cooled at theheat exchanger 902 is supplied to the temperature adjustment head 400″,then the used coolant passes through the tank 903 and is cooled again atthe heat exchanger 902.

Next, when the burn-in test ends, the pump 901 is stopped and the secondto fourth valves S2 to S4 are opened. Therefore, in this state, thecirculation route is blocked at the first valve S1. Instead, the openingof the second to fourth valves S2 to S4 causes the formation of arecovery route from the compressed gas supply apparatus 904 through thetemperature adjustment head 400″ to the tank 903. Further, when suppliedfrom the compressed gas supply apparatus 904 to that recovery route, thecoolant accumulated in the temperature adjustment head 400″ is pushedout by the compressed gas and recovered at the tank 903. After thecoolant finishes being recovered, all of the valves S1 to S4 are closed.

As explained above, in the burn-in system according to the thirdembodiment of the present invention, when pushing the cooling block 410″of the temperature adjustment block 400″ against a DUT, the coolantsupplied through the entrance side opening 4111″ of the entrance sidechannel 411″ is made to directly contact the surface of the DUT and thevalve 417″ is controlled to operate to enable the individual DUT to bedirectly adjusted in temperature. When simultaneously performing aburn-in test on a plurality of DUTs, it is possible to independently andaccurately control the temperature of each DUT.

Further, by providing the chiller 900″ with the above-mentionedrecovering means, it is possible to recover the coolant directlycontacting the DUTs after the end of the burn-in tests.

Note that the embodiments explained above were given for facilitatingunderstanding of the present invention and were not given for limitingthe present invention. Therefore, the elements disclosed in theembodiments include all design changes or equivalents falling under thetechnical scope of the present invention.

In the above embodiments, the burn-in system was explained as amonitored burn-in system, but the present invention is not particularlylimited to this. For example, it may also be a dynamic burn-in systemwhich applies power voltage to DUTs under a constant temperature andsupplies signals close to actual operation to the input circuits of theDUTs for screening or a static burn-in system which applies powervoltage to DUTs under a high temperature and sends a current through theDUTs to apply temperature and voltage stress to the DUTs for screening.General burn-in systems are included.

1. A burn-in system for conducting a burn-in test on a device under test(DUT) mounted on a burn-in board, comprising: a cooling block formedwith channel able to carry a coolant for cooling the DUT; a measurementblock having measuring device configured to measure the temperature ofthe DUT; and a variable flow rate device configured to vary the flowrate of the coolant flowing through the channel, bringing the coolingblock and the measurement block into contact with the DUT and conductinga burn-in test on the DUT, wherein the cooling block is formed with anaccommodating space for accommodating the measurement block, and themeasurement block is accommodated in the accommodating space having alayer of air formed between the measurement block and the cooling blockso as to be insulated from the cooling block.
 2. The burn-in system asset forth in claim 1, wherein the measurement block is supported andmechanically floating with respect to the cooling block, and when themeasurement block is not in contact with the DUT, a front end face ofthe measurement block sticks out relative to a front end face of thecooling block.
 3. The burn-in system as set forth in claim 2, whereinthe system further comprises a first biasing device provided between themeasurement block and the cooling block and configured to bias themeasurement block to the front end face.
 4. The burn-in system as setforth in claim 3, wherein when the measurement block is not in contactwith the DUT, the first biasing device cause the measurement block to bebiased and cause part of the measurement block to contact the coolingblock.
 5. The burn-in system as set forth in claim 1, wherein the systemfurther comprises: a plurality of temperature adjustment boardssupporting a plurality of the cooling blocks at a frame with mechanicalfloating; and a burn-in chamber able to hold the burn-in boards, whereineach of the temperature adjustment boards is provided in the burn-inchamber so that the each cooling block faces the DUT mounted on theburn-in board.
 6. The burn-in system as set forth in claim 5, whereinthe each cooling block is supported on the frame through a secondbiasing device configured to bias the cooling block toward a burn-inboard.
 7. The burn-in system as set forth in claim 5, wherein at leastpart of the channels formed at the plurality of the cooling blocks areconnected in series.
 8. The burn-in system as set forth in claim 7,wherein the cooling block has-a bypass for making the coolant bypass thechannel.
 9. The burn-in system as set forth in claim 8, wherein thevariable flow rate device is provided in the channel or the bypass. 10.The burn-in system as set forth in claim 8, wherein the temperatureadjustment board has first cooling blocks formed with the bypasses andsecond cooling blocks not formed with the bypasses.
 11. The burn-insystem as set forth in claim 8, wherein the plurality of temperatureadjustment boards include one temperature adjustment board which hasfirst cooling blocks formed with the bypasses and another temperatureadjustment board which has second cooling blocks not formed with thebypasses.
 12. The burn-in system as set forth in claim 5, wherein thetemperature adjustment board has at least two types of cooling blockshaving different thermal resistances between the coolant and the DUT.13. The burn-in system as set forth in claim 5, wherein a thermalresistance between the coolant and the DUT in coolant blocks of onetemperature adjustment board among the plurality of temperatureadjustment boards and a thermal resistance between the coolant and theDUT in coolant blocks of another temperature adjustment board among theplurality of temperature adjustment boards are different.
 14. Atemperature adjustment head comprising: a cooling block formed withchannels able to carry a coolant for cooling the device under test(DUT); a measurement block having a measuring device configured tomeasure a temperature of the DUT; and a variable flow rate deviceconfigured to vary the flow rate of the coolant flowing through thechannel, wherein the cooling block is formed with an accommodating spacefor accommodating the measurement block, and the measurement block isaccommodated in the accommodating space having a layer of air formedbetween the measurement block and the cooling block so as to beinsulated from the cooling block.